Amino acids are vital substances that are mostly ingested through food. There are hundreds of different amino acids, but in terms of diet and nutrition, there are only 22 you need to be concerned with. Collectively amino acids are used to support nearly every physiological function, including muscle growth and athletic endurance.
Dietary amino acids
The 22 amino acids that relate to diet and nutrition are called "standard amino acids." They're subdivided further into two groups: essential and nonessential.
Essential amino acids
There are nine essential amino acids. These must be taken in through food or supplementation since the body has no means of synthesizing them. They are:
|Essential amino acid||How it works|
|Histidine||Supports the central nervous and digestive systems.|
|Isoleucine*||Promotes the use of glucose and protein by the muscles during exercise, and regulates blood sugar levels.|
|Leucine*||Mostly used for protein synthesis in muscle tissues, but also improves glucose uptake and is necessary to form blood cells. This is our favorite amino acid due to its muscle-building and endurance-boosting effects.|
|Valine*||Converts fatty acids to energy and helps the digestive system absorb calcium.|
|Lysine||Converts fatty acids to energy and helps the digestive system absorb calcium.|
|Methionine||Very important to kidney cells, methionine is also a precursor of creatine, taurine, and lecithin.|
|Phenylalanine||Helps to regulate mood and cognitive function.|
|Threonine||Needed to form collagen and tooth enamel, it also supports the immune system.|
|Tryptophan||While it's probably most familiar as a sleep aid, tryptophan is also a precursor for the synthesis of auxin, niacin, and serotonin. It is also needed to regulate nitrogen levels.|
*Also known as branched-chain amino acids (BCAAs).
Nonessential amino acids
The remaining 13 amino acids are considered "nonessential" as the body can synthesize them from other sources. Serine
|Essential amino acid||How it works|
|Alanine||Used to form glucose in the liver, it's also needed for sugar and acid digestion and for immune system support.|
|Arginine||A necessary precursor for the nitric oxide synthesis, helps in both tissue and bone repair, supports the immune system, and removes ammonia from the body.|
|Asparagine||Aids in metabolic control of cell functions in nerve and brain tissue.|
|Aspartic acid||Is thought to be a neurotransmitter, but research is not yet conclusive.|
|Cysteine||A precursor to glutamic acid, glycine, and sulfide.|
|Glutamic acid||Necessary for metabolic function, removal of excess nitrogen and is the most common neurotransmitter in the body.|
|Glutamine||Needed for protein synthesis, pH balance in the kidneys, cellular energy, and as a transporter of nitrogen, carbon, and ammonia.|
|Glycine||Needed to digest proteins and is a common neurotransmitter.|
|Ornithine||Necessary to support the urea cycle and may also play a role in reducing the feeling of fatigue.|
|Proline||Needed for regular joint and tendon function and also for the formation of collagen.|
|Selenocysteine||Serves the same functions as cysteine but also plays a role in protein synthesis.|
|Serine||Needed for metabolic function and also functions as a neurotransmitter.|
|Tyrosine||Needed to synthesize melanin, epinephrine, and thyroid hormones.td>|
There are hundreds of different amino acids, but in terms of diet and nutrition, only 22 you need to be concerned with.
As far as diet goes, supplementation with essential amino acids is generally only necessary for certain medical conditions or to support a vegetarian/vegan diet.
The BCAAs can help to promote muscle growth and speed recovery, however, so you'll frequently see them included in pre-workout formulas and protein mixes. Supplements that emphasize BCAAs are usually formulated in a ratio that expresses how much relative leucine, isoleucine, and valine they have. For example, one common formulation you'll see in supplements is leucine in a 2:1:1 ratio. This simply means there's twice as much leucine as there are the other two BCAAs.
Glutamine is frequently featured in supplements under the claim that it is a vital muscle fuel source that is depleted by exercise. It's still unclear whether glutamine supplementation before or during a workout has any effect on muscle performance, however. Two placebo studies found no effect of glutamine supplementation whatsoever in weightlifting tests.[23,24] However, a study of long-distance runners found that glutamine seemed to bolster their strained immune systems after a marathon run.
Beta-alanine is a useful supplement for upping the intensity of your workout. It increases the availability of carnosine to muscle tissue. Carnosine regulates the pH balance of muscles by scooping up the hydrogen ions generated when they're in use, and this amounts to a boost in both muscle output and endurance. While there's no studies that have shown carnosine to directly influence the growth of muscles, supplementation does allow for longer sets at higher intensity. Concurrent carnosine supplementation is necessary to see this benefit, though - beta-alanine alone doesn't have any particular effect.
The L-carnitine family provides energy at a cellular level. It's made up of several sub-compounds that have different beneficial effects. Acetyl L-carnitine (ALCAR) is a neurotransmitter that improves cognitive function and reduces feelings of fatigue. Propionyl-L-carnitine (PLCAR) has been shown in rat studies to promote the burning of fat as energy to support working muscle tissue. L-carnitine L-tartrate is an antioxidant that eases soreness after exercise. And glycine propionyl-L-carnitine (GPLC) improves blood flow and oxygen delivery to muscle tissue.
Both the essential and the non-essential amino acids are found in foods that are rich in protein.
If you're meeting your overall daily nutritional requirements for protein and carbohydrates, your body will be able to synthesize all of the non-essential amino acids that it needs.
Meat, eggs, poultry, and fish are the best complete sources of the nine essential amino acids. Beans are also good sources, particularly pinto, kidney, and soy. A number of vegetables do contain complete proteins, but in much smaller amounts than other food sources.
Where to buy
You can find amino acid supplements here at PricePlow at 30% to 50% off of retail prices. We typically enjoy powdered-based formulas more, especially for workouts, since they are more convenient, tastier, and typically cost less per gram.
- PubChem; "Histidine;" 2014
- PubChem; "Isoleucine;" 2014
- PubChem; "Leucine;" 2014
- PubChem; "Lysine;" 2014
- PubChem; "Methionine;" 2014
- PubChem; "Phenylalanine;" 2014
- PubChem; "Threonine;" 2014
- PubChem; "Tryptophan;" 2014
- PubChem; "Valine;" 2014
- PubChem; "Alanine;" 2014
- PubChem; "Arginine;" 2014
- PubChem; "Asparagine;" 2014
- PubChem; "Aspartic Acid;" 2014
- PubChem; "Cysteine;" 2014
- PubChem; "Glutamic Acid;" 2014
- PubChem; "Glutamine;" 2014
- PubChem; "Glycine;" 2014
- PubChem; "Ornithine;" 2014
- PubChem; "Proline;" 2014
- PubChem; "Selenocysteine;" 2014
- PubChem; "Serine;" 2014
- PubChem; "Tyrosine" 2014
- Candow, D, et. al; European Journal of Applied Physiology; "Effect of glutamine supplementation combined with resistance training in young adults;" December 2001
- Antonio, J, et. al; Journal of Strength and Conditioning Research; "The effects of high-dose glutamine ingestion on weightlifting performance;" February 2002
- Castell, L, et. al; Nutrition; "The effects of oral glutamine supplementation on athletes after prolonged, exhaustive exercise;" July 1997